The present invention relates to apparatus for treating coronary or other vascular bifurcation lesions, and in particular to a stent used to treat the upstream vessel and/or the bifurcation region itself, and delivery systems to deploy this stent.
Stenotic lesions which develop in vascular disease commonly occur at bifurcations, where a parent vessel divides into two branch vessels. Such lesions are difficult to treat particularly as a result of the geometry of the bifurcation region itself, the fact that bifurcation lesions come in many shapes and forms and the fact that there can be many configurations of downstream vessels; the angles between the parent and down stream vessels can vary considerably.
Vascular stents are a typical form of treatment of such lesions. There are two common. forms of stent and deployment method:
(i) self-expanding stents, which are typically retained in their constrained form by a sheath or sleeve which is withdrawn to enable the stent to expand;
(ii) balloon expanded stents, which involve the mounting of the stent upon a balloon which is inflated to deploy the stent when the stent is located in the region to be treated.
Both forms of stent employ the use of guide wires to help locate the stent in the region to be treated before deployment.
Most stent designs in use are essentially cylindrical in shape with single transverse apertures at each end. When these stents are used in the generally angled region of a bifurcation then there is less than optimal vessel wall coverage as well as stent distortion particularly at the site of vessel bifurcation.
It is an object of the present invention to provide a stent which overcomes or at least ameliorates some of the abovementioned disadvantages or to at least provide the public with a useful choice.
Other objects of the invention may become apparent from the following description which is given by way of example only.
According to a first aspect of the invention there is provided a bifurcation stent open at a proximal end, having a closed terminus at a distal end, and apertures adjacent the closed terminus and at an angle in relation to the longitudinal axis of the stent.
Preferably the apertures include a first aperture and a second aperture substantially on opposite longitudinal sides of the stent.
Preferably the first aperture and the second aperture may have a common angle in relation to the longitudinal axis of the stent.
Preferably the bifurcation stent may be a self-expanding stent, or alternatively a balloon-inflated stent.
According to a second aspect of the invention there is provided a bifurcation stent adapted for use in an upstream vessel at a bifurcation capable of being positioned at the carina of the bifurcation substantially without extending into either downstream vessel.
According to a third aspect of the invention there is provided a stent delivery system adapted to deliver the balloon-inflated bifurcation stent of the first aspect of the invention including a balloon mechanism, the balloon mechanism forming one or more head portion at a distal end adapted to engage an aperture of the bifurcation stent, and the stent delivery system further including one or more lumen through the balloon mechanism and exiting from the or each head portion.
According to a fourth aspect of the invention there is provided a method of deploying a balloon inflatable stent at a bifurcation, including the steps of:
mounting a balloon deployed stent having a closed terminus at a distal end and first and second apertures adjacent the closed terminus on a balloon mechanism having a first head portion extending into the first aperture and a second head portion extending into the second aperture, a first guidewire passing through a lumen in the balloon mechanism exiting from the first head portion and a second guidewire passing through a lumen in the balloon mechanism and exiting from second head portion;
locating the first guidewire in a parent vessel with the first distal end of the guidewire extending beyond an ostium of a first downstream vessel;
locating the second guidewire in the parent vessel with the first distal end of the guidewire extending beyond an ostium of second downstream vessel;
advancing the balloon-inflatable stent along the guidewires in the parent vessel until the closed terminus abuts a carina at the bifurcation, with the first head portion of the balloon mechanism aligned with the ostium of the first downstream vessel and second head portion of the balloon mechanism aligned with the ostium of the second downstream vessel;
inflating the balloon mechanism to expand the stent, the first and second head portions of the balloon mechanism extending into their corresponding ostia.
According to a fifth aspect of the invention there is provided a stent delivery system adapted to deliver the self-expanding bifurcation stent of the first aspect of the invention, the system including an outer delivery sleeve adapted to constrain the self-expanding stent in restricted form and enable expansion of the stent by withdrawal of the sleeve; one or more lumens passing through the delivery sleeve and extending at least to the distal end of the delivery sleeve, the or each lumen adapted to house one or more guidewires and enable a guidewire to exit each aperture of the stent; and said sleeve not prohibiting the passage of the or each lumen and/or guidewire through the aperture.
Preferably the stent delivery system may further include locating means at the distal end of the delivery sleeve, the locating means adapted in use to position the closed terminus of the stent substantially opposed to the carina of the bifurcation.
According to a sixth aspect of the invention there is provided a method of deploying a self-expanding bifurcation stent, the method including the steps of:
housing an unexpanded bifurcation stent having a closed terminus at a distal end and first and second apertures adjacent to the closed terminus, in an outer delivery sleeve, the sleeve not occluding the first and second apertures,
mounting the unexpanded stent and its sleeve on first and second guidewires passing through one or more lumens through the delivery sleeve and extending at least to the distal end of the delivery sleeve, such that a guidewire exits each aperture;
locating the first guidewire in a parent vessel with its first distal end extending beyond an ostium of a first downstream vessel;
locating the second guidewire in a parent vessel with its first distal end extending beyond an ostium of a second downstream vessel;
advancing the stent and sleeve along the guidewires until the closed terminus of the stent is substantially opposed to the carina of the bifurcation, the apertures of the stent being aligned with the ostia of the downstream vessels;
deploying the stent by withdrawal of the delivery sheath, the apertures expanding and aligning with the ostia of the downstream vessels.
Preferably the method may further include the step of engaging locating means at the distal end of the delivery sleeve on the carina of the bifurcation prior to deploying the stent.
According to a seventh aspect of the invention there is provided an arrangement of stents in a bifurcation including the bifurcation stent of the first aspect of the invention located in the upstream vessel of the bifurcation with its closed terminus substantially opposed to the carina and at least one aperture aligned with an ostium of one downstream vessel; and at least one tubular stent located in a downstream vessel with a proximal aperture substantially aligned with the aperture of the bifurcation stent.
Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.